1. Field of the Invention
The present invention relates to a process for producing a new polyester copolymer, and more particularly, to a process for producing a polyester copolymer having a low melting point and a proper degree of crystallinity as compared with the conventional polyester copolymers.
2. Description of Prior Arts
Heretofore, linear polyester copolymers have found use in broad application areas such as films, moldings, and fibers. Generally speaking, some of such polyester copolymers have a high molecular weight and a high melting point if they have a proper degree of crystallinity, and they are not necessarily suitable for certain applications such as hot melt adhesives, binders for lamination, blending with other plastics, and polyester elastomers. In other words, what is required in such applications is usually a polyester copolymer having a comparatively low melting point and a proper degree of crystallinity.
Generally, a polyester copolymer is composed of a dicarboxylic acid component and a glycol component, and it is possible to vary the melting point and degree of crystallinity by selecting the kind of each of the two components. However, it is not uncommon that lowering the melting point is possible only with an extreme decrease in the degree of crystallinity; in an extreme case, the copolymer becomes amorphous. Thus it is difficult to balance the melting point with the degree of crystallinity.